Guidance systems for continuous mining machinery



M y ,1967 R. c. W. CROM mu 3,322,465

- GUIDANCE SYSTEMS FOR CONTINUOUS MINING. MACHINERY Filed Nov. 23, 1964 I ESheets-Shet 1 May 30, 1967' R. c. w. CROM ET AL I GUIDANCE SYSTEMS FOR CONTINUOUS MINING MACHINERY" Filed Nov. 23, 1964 ZSh ee tS-S heet 2 United States Patent 3,322,465 GUIDANCE SYSTEMS FOR CONTINUOUS MINING MACHINERY Russell C. W. Crom, Clinton, Iowa, and David M. Williams, Arlington Heights, 11]., assignors to International Minerals & Chemical Corporation, a corporation of New York Filed Nov. 23, 1964, Ser. No. 412,933 15 Claims. (Cl. 299-1) This invention relates to guidance systems for automatically controlling the operation of continuous mining machines.

With the advent of mechanization of the mining industry, automatic mining machinery has been introduced which continuously removes ore from the mineral-containing vein being mined. For example, in potash mining machinery has been introduced to continuously cut and remove ore from the working face in the mine. Such machines generally comprise self-propelled, tracked vehicles which support one or more rotating boring heads. These heads contain a plurality of bits adapted to continuously remove ore from the working face. The bits generally rotate in a circular course parallel with the working face. The machine advances slowly towards the working face as ore its removed and recovered.

Machines of this type are designed to cut or bore a continuous passage having a generally fiat floor and ceiling and having curved sides. Obviously, a number of parallel contiguous passes can be made with such machinery to form wide passages defining a mining pattern resembling the usual room and pillar pattern.

Such self-propelled, continuous mining machines are steered in the plane of the mine floor (which may or may not be horizontal) by retarding the motion of one of the two tracks of the machine, much in the same manner as a bulldozer is steered. It is also necessary to control the vertical path of the machine to prevent the machine from ascending aboveor descending below the path of the vein of ore mined. This is accomplished by making the cutting heads vertically adjustable so that they can be raised or lowered with respect to the floor upon which the machine stands. It will be understood that the ma chine in its cutting operation forms the floor over which the machine will advance, and that by raising or lowering the cutting head the path of the machine through the earth is effectively controlled. Such continuous mining or earth boring machines are described in considerable detail in the prior art, for example, US. Patent No. 2,826,402. Accordingly, a detailed description of such machinery will not be undertaken.

Continuous mining machines are usually steered by an operator who controls the improvement of the vehicle tracks and the elevation of the cutting head by means of a number of levers. The course which the machine will follow is accordingly determined by the judgment of the machine operator. It has been found in practice that it is difficult for a machine operator to maintain continuous mining machinery on a predetermined course over a substantial distance. This is due to the fact that there is in the mine no satisfactory reference from which the operator can judge the direction of travel of the machine.

It is an object of this invention to provide an automatic device for controlling the horizontal and vertical direction of cut of continuous mining machinery.

It is another object of this invention to provide a guidance system for continuous mining machinery which will make unnecessary the use of an operator to guide the machine.

Yet another object of this invention is to provide a guidance system for continuous mining machinery which will enable the machine to be directed over a predetermined path with minimum drift from the true bearing.

Briefly, the system of this invention comprises a flexible line secured at one end to a fixed point within the mine, and supported under tension at the other end from the continuous mining machine. Electrical means are provided for producing a signal in response to deviation of the direction of the line from a predetermined bearing. Means are also provided for producing a signal responsive to the deviation of the heading of the machine from the direction of the line. The signals thus generated are employed to operate an electromechanical device such as an electrically controlled valve, for steering the machine back to its true course and aligning it on a true hearing.

The invention will be describedin reference to the drawings, of which:

FIGURE 1 is an elevational view, in section, of a portion of the guidance apparatus of this invention,

FIGURE 2 is a view in the direction of 22 of FIG- URE 1,

FIGURE 3 is a schematic diagram of a circuit employed in the guidance system with this invention, and,

FIGURE 4 is a diagram employed to described the operation of the guidance system. 1

Referring to FIGURE 1, control case 10 contains a guidance pulley 12 which is supported upon axle 14. Line 16, which is preferably a fine steel wire, but which may also be a plastic monofilament line or braided line, enters case 10 through hole 18, passes over pulley 16 and is wound upon spool 20. Spool 20 is supported upon shaft 22, and is rotatable, but provided with tensioning means for maintaining a reasonably constant predetermined tension in line 16. For example, a friction drag against the spool may be employed to feed out line as the mining machine, upon which case 10 is supported, advances. Preferably, spring means (not shown), is employed in conjunction with the drum to maintain a predetermined tension in line 16. Devices for paying out line under tension are well known and in themselves are not the subject of the instant invention. Accordingly, they will not be described in detail. Variable resistances 22 and 24 are supported within case 10 by means of brackets 26 and 28 respectively.

Referring now to FIGURE 2 it will be seen that variable resistances 22 and 24 are provided with bifurcated arms 30 and 32, respectively. Line 16 passes between the tines of arms 30 and 32. The space between the tines is preferably sufiicient to provide a minimum of friction between the line and the tines, but without introducing unnecessary play. It will be understood that case 10 is secured to the continuous mining machine, preferably above about the longitudinal mid-point of the tracks of the machine. A similar equipped case, not shown, is supported at a fixed point in the mine. Line 16 runs between the two cases, and is stretched under sufficient tension to insure minimum sagging. It will be understood that it is not necessary to provide a pulley 12 and takeup spool 20 in both cases, it being sufficient that one of the cases be equipped as shown in FIGURE 1, the line merely being secured to a fixed point in the second case to correspond to the point of tangency between the line and pulley 12.

Looking briefly to FIGURE 4, it Will be seen that de viation of line 16 from its initial bearing 40 will result in a displacement of the bifurcated arm shown at 42 from position 44 to position 42. It will be seen that the displacement of the arm associated with the control case which is located at a fixed point in the mine is a measure of the deviation of the machine 46 from its true bearing 40. It will also be seen that displacement of the arm 50 from an initial position 48 is a measure of the deviation of the direction of cut or heading of machine 46, which is represented by direction 52, from line 16.

It will be understood that the movement of vertical arm 32 in response to horizontal angular deviation of the actual direction of line 16 from its initial bearing produces a change in the resistance of variable resistance 24 which is proportional to the magnitude of the angle of deviation, and which has a sense (increase or decrease in resistance) which is determined by the sense (right or left) of the angle of deviation 54 shown in FIGURE 4. Finally, considering the variable resistance and vertical arm in the control case mounted on the continuous mining machine, the change in resistance is a measure of the magnitude of the angular deviation of the heading of the machine from the actual direction of line 16.

It will be understood that a great variety of different sensing devices are available for producing an electrical signal in response to a change in position. Resistances have been described, but they are merely illustrative. It will be understood that any of the numerous devices for relating a change of position to a change in impedence, such as variable capacitors, variable inductance coils, and the like may be used. Other sensing devices may be used, for example, differential transformers. While the present invention will be illustrated by the description of a system which employs variable resistances as the sensors,-it will be understood that the invention contemplates the use of other conventional sensing devices as well. Certain circuit modifications will be required depending upon the particular sens-or employed. Such modifications of the ex emplary circuit hereinafter described will be apparent to those skilled in the art.

Referring now to FIGURE 3, Wheatstone bridge circuit 60 is made up of four variable resistances serially connected in closed circuit as shown. Variable resistance 24, which supports the substantially vertical arm 32 and which will be considered to be contained in the control case secured to the continuous mining machine, is connected as one of the resistances of bridge circuit 60 as shown. Variable resistance 62 of FIGURE 3 will be considered to be the corresponding variable resistance in the control case which is secured in fixed position in the mine. Considering both variable resistances to be constructed such that, when viewed from behind both control cases, rotation of the arms connected to the resistances in a clockwise direction results in a resistance change of the same sense, i.e., a resistance increase in each case, variable resistances 24 and 62 will be positioned opposite each other in the bridge circuit as shown. Where rotation of the variable resistance as described would result in an increase in resistance of one variable resistance and a decrease in resistance for the other, the two variable resistances should be connected in the bridge circuit as adjacent arms, rather than as opposite arms. A direct potential is applied across points 64 and 66 of the bridge. Accordingly, if an imbalance in the bridge circuit exists a potential will develop across points 68 and 70. This potential, depending upon its polarity, will energize one of relays 72 and 74, but not both, due to the action of rectifiers 76 and 78. Thus, for example, if point 70 is more positive, relay 74 will close but relay 72 will remain open. In the absence of bridge unbalance, both relays will be opened. The relay contacts are connected to a potential source and to motor 80 of motor controlled valve 82. The operation of valve 82, which is a three-way valve, is such that fluid can enter the valve through openings 84 or 86, and be discharged through opening 88, depending upon the position of the valve. Clockwise rotation of the motor from a predetermined neutral position will, for example, cause valve inlet 84 to be connected to the outlet 88. Counterclockwise rotation of motor 80 from the predetermined position will cause the valve to connect inlet 86 to outlet 88. In the neutral position, the valve is closed both ways. The motor 80 is equipped with a threaded shaft 90 which supports a no nr-otating collar 92. This collar in turn supports brush 94 which contacts resistance element 96, forming a variable resistance 98, which is connected in the bridge circuit as shown.

Valve 82 is connected to the hydraulically-operated drive of the continuous mining machine such that fluid is bled from the drive system through valve 82 and back to the hydraulic reservoir. Thus, when the valve 82 is positioned to connect inlet 84 t0 outlet 88 hydraulic fluid is bled from the drive mechanism from the left-hand track and rotation of that track relative to the right-hand track is retarded. Similarly, if inlet 86 is connected to outlet 88 the rotation of the right-hand track relative to the lefthand track is retarded. It will be seen that an imbalance in the bridge circuit 60 results in a retardation of the rotation of either the right-hand or left-hand track, depending upon the polarity of the unbalance. For purpose of illustration it will be considered that the connections to motor are such that when point 68 of the bridge circuit is more positive than point 70 the rotation of the right-hand track of the vehicle is retarded, and that when point 70 is more positive than point 68 the rotation of the left-hand track is retarded.

In operation, the continuous mining machine which supports control case 10 is positioned and aligned to make a cut. A second control case similar to control case 10 is positioned at a fixed point 2.0 feet to the rear of the continuous mining machine. The location of the second control case is selected such that the initial direction of line 16 which extends between the control cases defines the bearing which the machine is to follow. With the machine and control cases thus aligned to start a cut variable resistance of bridge circuit 60 is adjusted so that the bridge circuit is balanced and valve 82 is closed to flow in both directions. Assuming now that the mining machine, after a period of operation, has deviated from its initial bearing as represented by bearing 40 of FIGURE 4, to a position to the right of bearing 40, the direction of line 16 will deviate from bearing 40 by an angle 54, and this deviation of the line will result in a movement of the vertical potentiometer arm in the potentiometer in the fixed control case, resulting in an increase in variable resistance 62 of the bridge circuit. Thus, point 70 will be more positive than point 68, relay 74 will close and valve inlet 84 of the control valve will be connected to the valve discharge, retarding the rotation of the left-hand tread of the continuous mining machine. It will be seen that but for the action of variable resistance 98, the rotation of the left-hand tread will be retarded until the continuous mining machine turns sufficiently to produce an angle of deviation 48 between the heading 52 of the continuous mining machine and the direction of line 16 such as will give a decrease in the value of variable resistance 24 which will restore the balance of the bridge circuit. When bridge circuit balance is restored the heading of the continuous mining machine is in a direction to intersect the initial true bearing 40. If the mining machine advances on heading 52 the angle of deviation 54 will decrease, resulting in a decrease in the resistance of variable resistance 6-2. This results in an unbalancing of the bridge circuit making point 68 more positive than point 70, and retarding the rotation of the right-hand tread until a new heading is established such as will provide an angle of deviation 48 such that the value of variable resistance 24 is increased sufliciently to re-establish the balance of the bridge circuit. As the mining machine approaches the true bearing 40, the angle of deviation 48 decreases, line 16 approaches coincidence with initial bearing 40, and heading 52 approaches the parallel with initial bearing 40. Accordingly, it will be seen that the use of the control system is to cause the path of the continuous mining machine all ways to approach the bearing 40 asymptotically. The construction of variable resistances 24 and 62 should be such that for any unit angular deviation 54, the resulting percent change in impedance is greater, say by a factor of ten, than the impedance change resulting from a unit angular deviation 48. Thus, to restore balance to the bridge, angle 48 must be much larger than angle 54.

The operation of the system as described is modified by the incorporation of variable resistance 98 into the bridge circuit. Movement of the variable resistance 98 from a predetermined position corresponding to the valve position in which both inlets are blocked results in an increase or decrease in the value of variable resistance 98 such that the unbalance in the bridge circuit is in part compensated. Thus, the function of variable resistance 98 is to modify the operation of the circuit to prematurely restore bridge balance. In this manner excessive hunting of the system is prevented, without unnecessary sacrifice of sensitivity.

When the position of the continuous mining machine is along the true bearing 40 but the heading 52 does not correspond with the direction of line 16, i.e., the machine is correctly positioned but incorrectly headed, the movement of the variable resistance is to unbalance the bridge to retard tr'ead rotation and correct the heading of the machine to correspondwith the initial bearing.

In the foregoing description the guidance of the continuous miner in a horizontal plane was discussed. The action of variable resistance 22 (and a corresponding resistance in the second control case) were not discussed. It will be understood that an identical bridge circuit and control system is employed to control the position of the boring head of the machine, whereby the path of the machine in the vertical direction is controlled. If the position of the cutting heads is maintained hydraulically, a system employing an electrical actuated control valve can be used in the vertical system also.

It will be apparent to those skilled in the art that a wide variety of electro-mechanical devices can be used to convert the electrical output of the bridge circuit into mechanical motion, whereby the course of a vehicle is controlled. The most suitable electro-mechanical device for a given application will, of course, depend upon the mechanical details of the self-propelled machine which is to be guided.

While the invention has been described and illustrated with reference to a specific embodiment employing an illustrative electrical network and a specific device for converting electrical input into mechanical motion, it will be understood that within the scope of the appended claims the invention can be practiced otherwise than as specifically described.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a guidance system' for a selfapropelled vehicle, a

I flexible line, means for suspending said line under tension between a first point on said vehicle and a second fixed point remote from said vehicle, whereby said line determines an initial bearing, first means remote from said vehicle which is responsive to angular deviation of said'line from said initial bearing in a first plane substantially parallel to the ground plane of said vehicle for producing a first electrical signal having a sense indicative of the direction of deviation, second means on said vehicle which is responsive to an angular deviation of the heading of said vehicle from said line in said first plane for producing a second electrical signal having a sense indicative of the direction of deviation, and means responsive to said first and second signals for urging said vehicle to a heading'fwhich intercepts said initial bearing, and then urging said vehicle toward a bearing corresponding to the direction of said line.

2. An apparatus in accordance with claim 1 in which said vehicle is an earth-boring machine which includes vertically adjustable. boring means, and including third means remote froinsaid vehicle responsive to angular deviation of said line. from said bearing in a second plane substantially perpendicular to the ground plane and parallel with said initialbejaring for producing a third electrical signal having a sense indicative of the direction of deviation, fourth means on said vehicle which is responsive to angular deviation of the heading of said vehicle from said line in said second plane from producing a fourth electrical signal having a sense indicative of the direction of deviation and means responsive of said third and fourth signals for controlling said boring means to form a passage having a floor inclined to intersect said bearing, and then for controlling said boring means to form a passage having a floor parallel to the direction of said line. Y

3. An apparatus in accordance with claim 1 in which said means for producing a first electrical signal comprises a first variable irnpedence device actuated by change in angular orientation of said line to the earth.

4. An apparatus in accordance with claim 3 in which said means for producing a second electrical signal comprises a second variable impedance device actuated by change in angular orientation of said line to said vehicle.

5. An apparatus in accordance with claim 4 in which said first and second variable impedance devices are connected as branches of a four-branch Wheatstone bridge such that unbalance of the bridge resulting from positive angular deviation of said line from said original bearing is offset by negative angular deviation of the heading of said vehicle from said line.

6. An apparatus in accordance with claim 5 in which said first and second variable impedances are constructed such that the percent of impedance change resulting in a unit angular deviation of said line from said original bearing is substantially greater than the percent of impedance change resulting from a unit angular deviation of the heading of said vehicle from said line.

7. In combination with a self-propelled, tracked, continuous mining machine, a guidance system comprising a flexible line, means for suspending said line under tension between a first point on said vehicle and a second fixed point remote from said vehicle, whereby said line determines an initial bearing, first means remote from said vehicle which is responsive to angular deviation of said line from said initial bearing in a first plane substantially parallel to the ground plane of said vehicle for producing a first electrical signal having a sense indicative of the direction of deviation, second means on said vehicle which is responsive to angular deviation of the heading of said vehicle from said line in said first plane for producing a second electrical signal having a sense indicative of the direction of deviation, and means responsive to said first and second signals for urging said vehicle to a heading which intercepts said initial bearing, and then urging said vehicle toward a bearing corresponding to the direction of said line.

8. An apparatus in accordance with claim 7 in which said vehicle is an earth-boring machine which includes vertical adjustable boring means, including third means remote from said vehicle responsive to angular deviation of said line from said bearing in a second plane substantially perpendicular to the ground plane and parallel with said initial bearing for producing a third electrical signal having a sense indicative of the direction of de.

viation, fourth means on said vehicle which is responsive to angular deviation of the heading of said vehicle from said line in said second plane for producing a fourth electrical signal having a sense indicative of the direction of deviation and means responsive to said third and fourth signals for controlling said boring means to form a passage having a floor inclined to intersect said bearing, and then for controlling said boring machine to form a passage having a floor parallel to the direction of said line.

9. An apparatus in accordance with claim 7 in which said means for producing a first electrical signal comprises a first variable impedance device actuated by change in angular orientation of said line to the earth.

10. An apparatus in accordance with claim 9 in which said means for producing a second electrical signal comprises a second variable impedance device actuated by change in angular orientation of said line to said vehicle.

11. An apparatus in accordance with claim 10 in which said first and second variable impedance devices are connected as branches of a four-branch Wheatstone bridge such that unbalance of the bridge resulting from positive angular deviation of said line from said original bearing is ofiset by negative angular deviation of the heading of said vehicle from said line.

12. An apparatus in accordance with claim 11 in which said first and second variable impedances are constructed such that the percent of impedance change resulting in a unit angular deviation of said line from said original bearing is substantially greater than the percent of impedance change resulting from a unit angular deviation of the heading of said vehicle from said line.

13. An apparatus in accordance with claim 12 in which said means responsive to said first and second signals includes an electro-mechanical device for retarding the rotation of a first track of said vehicle relative to the rotation of a second track of said vehicle in response to an output of said bridge circuit of positive sense, and for retarding the rotation of the second track relative to the rotation of the first track in response to an output of negative sense. 14. An apparatus in accordance with claim 13 in Which the magnitude of tread rotation retardation is proportional to the magnitude of the output of said bridge circuit.

15. An apparatus in accordance with claim 14 including a third variable impedance device actuated by said electro-mechanical device to produce an impedance change in proportion to the magnitude of retardation of rotation produced by said electro-mechanical device, said third variable impedance being connected as an arm of said bridge circuit, whereby actuation of said electro-mechanical device acts to restore balance to said bridge circuit.

References Cited UNITED STATES PATENTS 2,761,666 9/1956 Heimaster et a1. 299-1 2,789,649 4/1957 Seitzer 18079.1

ERNEST R. PURSER, Primary Examiner.

CHARLES E. OCONNELL, Examiner. 

1. IN A GUIDANCE SYSTEM FOR A SELF-PROPELLED VEHICLE, A FLEXIBLE LINE, MEANS FOR SUSPENDING SAID LINE UNDER TEN SION BETWEEN A FIRST POINT ON SAID VEHICLE AND A SECOND FIXED POINT REMOTE FROM SAID VEHICLE, WHEREBY SAID LINE DETERMINES AN INITIAL BEARING, FIRST MEANS REMOTE FROM SAID VEHICLE WHICH IS RESPONSIVE TO ANGULAR DEVIATION OF SAID LINE FROM SAID INITIAL BEARING IN A FIRST PLANE SUBSTANTIALLY PARALLEL TO THE GROUND PLANE OF SAID VEHICLE FOR PRODUCING A FIRST ELECTRICAL SIGNAL HAVING A SENSE INDICATIVE OF THE DIRECTION OF DEVIATION, SECOND MEANS ON SAID 